1. The Field of the Invention
The present invention relates to tires mounted on wheels and intended to be capable of bearing a substantial load without inflation pressure, referred to as non-pneumatic tires.
2. The Related Art
Patent application WO 00/37269, corresponding to U.S. patent application Ser. No. 09/466,524, filed Dec. 17, 1999, proposes such an elastic non-pneumatic tire. It describes a load-bearing structure essentially comprising a plurality of support elements arranged substantially radially, cyclically symmetrically all around the circumference of the tire. When the non-pneumatic tire described in patent application WO 00/37269 bears a load, a certain number of support elements present in the contact area are subjected to major flexing, which makes it possible for them to develop a force of taking up part of the load. An interconnection structure makes the support elements work together, transferring the stresses to the adjacent support elements. The ability of this tire to bear a certain load comes from the flexural stressing of the support elements present in the contact area of the elastic non-pneumatic tire, and it also comes from the like flexural stressing of the support elements outside the contact area of the elastic non-pneumatic tire, via the interconnection structure.
Finally, according to the teaching of the aforementioned patent application WO 00/37269, in the area of contact with the ground, there is a difference in flexion (radially) between adjacent support elements. It is also known that each of the support elements is capable of withstanding the torsion and that, before penetrating into the contact area, the support elements undergo a certain deradialisation. During travel in normal operation of the tire, the penetration of the support elements into the contact area is somewhat retarded, which causes gradual deradialisation. Then, as the support elements cross the contact area, they readopt a radial position and, upon emerging from the contact area, they undergo substantially symmetrical deradialisation of the first deradialisation, relative to the vertical plane passing through the axis of rotation of the tire.
As for the interconnection structure, while being capable of transmitting part of the stress on the support elements to the adjacent support elements, it is known that it is sufficiently flexible to permit displacements of the support elements relative to each other, not only in the radial direction but also in the circumferential direction. The difference in displacement of the support elements in the radial direction corresponds to a difference in bending stress thereof. The difference in displacement in the circumferential direction corresponds to a circumferential stress on the interconnection structure, as evidenced by the deradialisation.
Although the elastic non-pneumatic tire proposed proves perfectly capable of withstanding a large load during normal operation, the aim of the present invention is to improve the load-bearing structure proposed so as to impart thereto considerably improved endurance, while retaining its very great ability to support the load.